Functionalized polymers and improved tires therefrom

ABSTRACT

A tire component comprising a vulcanized rubber deriving from a functionalized polymer defined by the formula I 
                         
where π is a polymer chain, B is a boron atom, R 1  is a bond or a divalent organic group, and each υ is independently selected from alkoxy groups (—OR), thioalkoxy groups (—SR), amino groups (—NR 2 ), or phosphino groups (—PR 2 ), where each R is independently selected from monovalent organic groups or two R groups form a divalent organic group, which forms a cyclic structure.

This application claims the benefit of U.S. Provisional Application No.60/591,065, filed Jul. 26, 2004.

FIELD OF THE INVENTION

One or more embodiments of this invention relates to functionalizedpolymers and their use in the manufacture of tires.

BACKGROUND OF THE INVENTION

In the art of making tires, IT may be desirable to employ rubbervulcanizates that demonstrate reduced hysteresis loss, i.e., less lossof mechanical energy to heat. Hysteresis loss can be attributed topolymer free ends within the cross-linked rubber network, as well as thedisassociation of filler agglomerates. The degree of dispersion offiller within the vulcanizate can also be a factor because increaseddispersion may provide better wear resistance.

Functionalized polymers have been employed to reduce hysteresis loss andincrease bound rubber. The functional group of the functionalizedpolymer is believed to reduce the number of polymer free ends viainteraction with filler particles. Also, this interaction reduce filleragglomeration, which can thereby reduce hysteretic losses attributableto the disassociation of filler agglomerates (i.e., Payne effect).

Conjugated diene monomers can be anionically polymerized by usingalkyllithium compounds as initiators. Selection of certain alkyllithiumcompounds can provide a polymer product having functionality at the headof the polymer chain. A functional group can also be attached to thetail end of an anionically-polymerized polymer by terminating a livingpolymer with a functionalized compound.

For example, trialkyltin chlorides, such as tributyl tin chloride, havebeen employed to terminate the polymerization of conjugated dienes, aswell as the copolymerization of conjugated dienes and vinyl aromaticmonomers, to produce polymers having a trialkyltin functionality at thetail end of the polymer. These polymers have proven to betechnologically useful in the manufacture of tire treads that arecharacterized by improved traction, low rolling resistance, and improvedwear.

Because functionalized polymers are advantageous, especially in thepreparation of tire compositions, there exists a need for additionalfunctionalized polymers. Moreover, because precipitated silica has beenincreasingly used as reinforcing particulate filler in tires,functionalized elastomers having affinity to silica filler are needed.

SUMMARY OF THE INVENTION

In general the present invention provides a tire component comprising avulcanized residue of a functionalized polymer defined by the formula I

where π is a polymer chain, B is a boron atom, R¹ is a bond or adivalent organic group, and each υ is independently selected from alkoxygroups (—OR), thioalkoxy groups (—SR), amino groups (—NR₂), or phosphinogroups (—PR₂), where each R is independently selected from monovalentorganic groups or two R groups form a divalent organic group, whichforms a cyclic structure.

The present invention also includes a tire component prepared by aprocess comprising vulcanizing a rubber formulation comprising avulcanizable rubber and a filler, where the vulcanizable rubber includesa functionalized polymer that is defined by the formula I

where π is a polymer chain, B is a boron atom, R¹ is a bond or adivalent organic group, and each υ is independently selected from alkoxygroups (—OR), thioalkoxy groups (—SR), amino groups (—NR₂), or phosphinogroups (—PR₂), where each R is independently selected from monovalentorganic groups or two R groups form a divalent organic group, whichforms a cyclic structure.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In one or more embodiments, the functionalized polymers that are usefulin the manufacture of tires include a boron atom or functionality at ornear at least one end of a polymer chain. In one embodiment, thefunctionalized polymers are employed in the manufacture of tire treadsand as a result tires having reduced rolling resistance can be prepared.

In one or more embodiments, the functionalized polymers can be definedby the formula I

where π is a polymer chain, B is a boron atom, R¹ is a bond or adivalent organic group, and each υ is independently selected from alkoxygroups (—OR), thioalkoxy groups (—SR), amino groups (—NR₂), or phosphinogroups (—PR₂), where each R is independently selected from monovalentorganic groups or two R groups form a divalent organic group, whichforms a cyclic structure.

In one embodiment, where both υ groups are alkoxy groups (—OR), thefunctionalized polymer can be defined by the formula 1A.

where π is a polymer chain, R¹ is a bond or a divalent organic group, Bis a boron atom, O is an oxygen atom, and each R² is independently amonovalent organic group or two R² groups join to form a divalentorganic group, which forms a cyclic structure.

In another embodiment, where both υ groups are thioalkoxy groups (—SR),the functionalized polymer can be defined by the formula 1B

where π is a polymer chain, R¹ is a bond or a divalent organic group, Bis a boron atom, S is an sulfur atom, and each R² is independently amonovalent organic group or two R² groups join to form a divalentorganic group, which forms a cyclic structure.

In still another embodiment, where both υ groups are amino groups(—NR₂), the functionalized polymer can be defined by the formula 1C

where π is a polymer chain, R¹ is a bond or a divalent organic group, Bis a boron atom, N is a nitrogen atom, and each R³ is independently amonovalent organic group or two R³ groups join to form a divalentorganic group, which forms a cyclic structure, each R⁴ is independentlya monovalent organic group or two R⁴ groups join to form a divalentorganic group, which forms a cyclic structure, or where one R³ and oneR⁴ group join to form a divalent organic group, which forms a cyclicstructure.

In yet another embodiment, where both υ groups are phosphino groups(—PR₂), the functionalized polymer can be defined by the formula 1D

where π is a polymer chain, R¹ is a bond or a divalent organic group, Bis a boron atom, P is an phosphorous atom, and each R³ is independentlya monovalent organic group or two R³ groups join to form a divalentorganic group, which forms a cyclic structure, each R⁴ is independentlya monovalent organic group or two R⁴ groups join to form a divalentorganic group, which forms a cyclic structure, or where one R³ and oneR⁴ group join to form a divalent organic group, which forms a cyclicstructure.

The polymer chain (π) of the functionalized polymer may include arubbery polymer. In one embodiment, the polymer chain substituentincludes a polymer that has a glass transition temperature (Tg) that isless than 0° C., in other embodiments less than −20° C., and in otherembodiments less than −30° C. In one or more embodiments, the rubberypolymer chain exhibits a single glass transition temperature.

In one or more embodiments, the polymer chain includes anionicallypolymerized polymers. Examples of these polymers include polybutadiene,polyisoprene, poly(styrene-co-butadiene),poly(styrene-co-butadiene-co-isoprene), poly(isoprene-co-styrene), andpoly(butadiene-co-isoprene).

In one or more embodiments, the polymer substituent may be characterizedby a number average molecular weight (M_(n)) of from about 5 to about1,000 kg/mole, in other embodiments from about 50 to about 500 kg/mole,and in other embodiments 100 to about 300 kg/mole, as measured by usingGel Permeation Chromatography (GPC) calibrated with polystyrenestandards and adjusted for the Mark-Houwink constants for the polymer inquestion.

The divalent organic group can include a hydrocarbylene group orsubstituted hydrocarbylene group such as, but not limited to, alkylene,cycloalkylene, substituted alkylene, substituted cycloalkylene,alkenylene, cycloalkenylene, substituted alkenylene, substitutedcycloalkenylene, arylene, and substituted arylene groups, with eachgroup preferably containing from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to about 20 carbonatoms. Substituted hydrocarbylene group includes a hydrocarbylene groupin which one or more hydrogen atoms have been replaced by a substituentsuch as an alkyl group. The divalent organic groups may also contain oneor more heteroatoms such as, but not limited to, nitrogen, oxygen,boron, silicon, sulfur, and phosphorus atoms.

The monovalent organic groups may include hydrocarbyl groups orsubstituted hydrocarbyl groups such as, but not limited to alkyl,cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl, substitutedcycloalkenyl, aryl, allyl, substituted aryl, aralkyl, alkaryl, andalkynyl groups, with each group preferably containing from 1 carbonatom, or the appropriate minimum number of carbon atoms to form thegroup, up to 20 carbon atoms. These hydrocarbyl groups may containheteroatoms such as, but not limited to, nitrogen, boron, oxygen,silicon, sulfur, and phosphorus atoms. In one or more embodiments,monovalent organic groups will not react with a living polymer.

In one or more embodiments, the functionalized polymer includes afunctional group at the head of the polymer; i.e., at an end other thanthat including the boron atom or functionality. This functionalizedpolymer can be defined by the formula II

where α includes a functionality or functional group that reacts orinteracts with rubber or rubber fillers or otherwise has a desirableimpact on filled rubber compositions or vulcanizates, π is a polymerchain, B is a boron atom, and υ is independently selected from alkoxygroups (—OR), thioalkoxy groups (SR), amino groups (—NR₂), or phosphinogroups (—PR₂), where each R is independently selected from monovalentorganic groups or two R groups form a divalent organic group, whichforms a cyclic structure.

Those groups or substituents that react or interact with rubber orrubber fillers or otherwise have a desirable impact on filler rubbercompositions or vulcanizates include known substituents such as trialkyltin substituents, cyclic amine groups, or sulfur-containingheterocycles. Exemplary trialkyl tin substituents are disclosed in U.S.Pat. No. 5,268,439, which is incorporated herein by reference. Exemplarycyclic amine groups are disclosed in U.S. Pat. Nos. 6,080,853,5,786,448, 6,025,450, and 6,046,288, which are incorporated herein byreference. Exemplary sulfur-containing heterocycles are disclosed in WO2004/020475, which is incorporated herein by reference.

The functionalized polymers may be prepared by reacting or terminating aliving polymer with an organoboron compound.

Organoboron compounds include those defined by the formula IIIR ³ _(3-n) B(

)_(n)where each

is independently selected from alkoxy groups (—OR), thioalkoxy groups(—SR), amino groups (—NR₂), or phosphino groups (PR₂), where each R isindependently a monovalent organic group or two R groups form a divalentorganic group, which forms a cyclic structure, each R³ is independentlya monoorganic group, a halide, or two R³ groups form a divalent organicgroup, which forms a cyclic structure, and n is an integer from 1 to 3.Useful halides include bromine and chlorine.

Types of organoboron compounds include alkoxyboranes, thioalkoxyboranes,aminoboranes, phosphinoboranes, and mixes thereof.

Examples of trialkoxyboranes include triethoxyborane,tri-n-propoxyborane, tri-isopropoxyborane, tri-n-butoxyborane,tri-t-butoxyborane, tripentoxyborane, trihexoxyborane, triheptoxyborane,triphenoxyborane, and mixtures thereof.

Examples dialkoxyalkyl boranes include diethoxyethylborane,dipropoxypropylborane, di-n-butoxybutylborane, di-t-butoxypropylborane,dipentoxyethylborane, diisoproxybutylborane, diphenoxyphenylborane,diphenoxypropylborane, and mixtures thereof.

Examples of alkoxydialkylboranes include diethylethoxyborane,diethylpropoxyborane, dibutylpropoxyborane, diisopropylisopropoxyborane,t-butoxydiisopropylborane, n-butoxydi-n-butylborane,t-butoxydi-t-butylborane, dipropylpentoxyborane, dipentylpentoxyborane,diphenylphenoxyborane, and mixtures thereof.

Examples dialkoxyhaloboranes include chlorodiethoxyborane,bromodipropoxyborane, chloro-di-n-butoxyborane, bromo-di-t-butoxyborane,chloro-dipentoxyborane, bromo-diisoproxyborane, chloro-diphenoxyborane,bromo-diphenoxyborane, and mixtures thereof.

Types of thioalkoxyboranes include trithioalkoxyboranes,dithioalkoxyalkylboranes, thioalkoxydialkylboranes, anddithioalkoxyhaloboranes.

Examples of trithioalkoxyboranes include trithioethoxyborane,trithio-n-propoxyborane, trithioisopropoxyborane,trithio-n-butoxyborane, trithio-t-butoxyborane, trithiopentoxyborane,trithiohexoxyborane, trithioheptoxyborane, trithiophenoxyborane, andmixtures thereof.

Examples of dithioalkoxyalkyl boranes include dithioethoxyethylborane,dithiopropoxypropylborane, butyldithio-n-butoxyborane,dithio-t-butoxypropylborane, dithiopentoxyethylborane,butyldithioisopropoxyborane, dithiophenoxyphenylborane,dithiophenoxypropylborane, and mixtures thereof.

Examples of thioalkoxydialkylboranes include diethylthioethoxyborane,diethylthiopropoxyborane, dibutylthiopropoxyborane,diisopropylthioisopropoxyborane, diisopropylthio-t-butoxyborane,di-n-butyl-thio-n-butoxyborane, di-t-butylthio-t-butoxyborane,dipropylpentoxyborane, dipentylthiopentoxyborane,diphenylthiophenoxyborane, and mixtures thereof.

Examples of dithioalkoxyhaloboranes include chlorodithioethoxyborane,bromodithiopropoxyborane, chlorodithio-n-butoxyborane,bromodithio-t-butoxyborane, chlorodithiopentoxyborane,bromodithioisopropoxyborane, chlorodithiophenoxyborane,bromodithiophenoxyborane, and mixtures thereof.

Types of aminoboranes include tris(dialkylamino)boranes,bis(dialkylamino) alkylboranes, and bis(dialkylamino)haloboranes.

Examples of tris(dialkylamino)boranes include tris (diethylamino)borane,tris(dipropylamino)borane, tris(di-n-butylamino)borane, tris(di-t-butylamino)borane, tris (diphenylamino)borane,tris(diphenylamino)borane, and mixtures thereof.

Examples of bis(dialkylamino)alkylboranes include bis(diethylamino)ethylborane, bis(dipropylamino) propylborane,bis(di-n-butylamino)butylborane, bis(di-t-butylamino)-t-butylborane,bis(dipentylamino)pentylborane, bis(diphenylamino)phenylborane,bis(diethylamino) propylborane, bis(dipropylamino)butylborane,bis(di-n-butylamino)propylborane, bis(di-t-butylamino)ethylborane,bis(dipentylamino)propylborane, bis(diphenylamino)ethylborane, andmixtures thereof.

Examples of bis(dialkylamino)haloboranes include bis(diethylamino)chloroborane, bis(dipropylamino)bromoborane,bis(di-n-butylamino)chloroborane, bis(di-t-butylamino)bromoborane,bis(diphenylamino) chloroborane, bis(diphenylamino)bromoborane, andmixtures thereof.

Types of phosphinoboranes include tris(dialkylphosphino)boranes,bis(dialkylphosphino)alkylboranes, and bis(dialkylphosphino)haloboranes.

Examples of tris(dialkylphosphino)boranes includetris(diethylphosphino)borane, tris(dipropylphosphino)borane,tris(di-n-butylphosphino)borane, tris(di-t-butylphosphino)borane,tris(diphenylphosphino)borane, tris(diphenylphosphino)borane, andmixtures thereof.

Examples of bis(dialkylphosphino)alkylboranes includebis(diethylphosphino)ethylborane, bis(dipropylphosphino)propylborane,bis(di-n-butylphosphino)butylborane,bis(di-t-butylphosphino)-t-butylborane,bis(dipentylphosphino)pentylborane, bis(diphenylphosphino)phenylborane,bis(diethylphosphino)propylborane, bis(dipropylphosphino)butylborane,bis(di-n-butylphosphino)propylborane,bis(di-t-butylphosphino)ethylborane, bis(dipentylphosphino)propylborane,bis(diphenylphosphino) ethylborane, and mixtures thereof.

Examples of bis(dialkylphosphino)haloboranes includebis(diethylphosphino)chloroborane, bis(dipropylphosphino)bromoborane,bis(di-n-butylphosphino)chloroborane,bis(di-t-butylphosphino)bromoborane, bis(diphenylphosphino)chloroborane,bis(diphenylphosphino)bromoborane, and mixtures thereof.

Examples of cyclic boranes include trimethylboroxine and B-methoxycatechol boranes.

Living polymers include anionically polymerized polymers.Anionically-polymerized living polymers may be formed by reactinganionic initiators with certain unsaturated monomers to propagate apolymeric structure. Throughout formation and propagation of thepolymer, the polymeric structure may be anionic and “living.” A newbatch of monomer subsequently added to the reaction can add to theliving ends of the existing chains and increase the degree ofpolymerization. A living polymer, therefore, includes a polymericsegment having a living or reactive end. Anionic polymerization isfurther described in George Odian, Principles of Polymerization, ch. 5(3^(rd) Ed. 1991), or Panek 94 J. Am. Chem. Soc., 8768 (1972), which areincorporated herein by reference.

Monomers that can be employed in preparing an anionically polymerizedliving polymer include any monomer capable of being polymerizedaccording to anionic polymerization techniques. These monomers includethose that lead to the formation of elastomeric homopolymers orcopolymers. Suitable monomers include, without limitation, conjugatedC₄-C₁₂ dienes, C₈-C₁₈ monovinyl aromatic monomers, and C₆-C₂₀ trienes.Examples of conjugated diene monomers include, without limitation,1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and1,3-hexadiene. A non-limiting example of trienes includes myrcene.Aromatic vinyl monomers include, without limitation, styrene, α-methylstyrene, p-methylstyrene, and vinylnaphthalene. When preparingelastomeric copolymers, such as those containing conjugated dienemonomers and aromatic vinyl monomers, the conjugated diene monomers andaromatic vinyl monomers can be used at a ratio of 95:5 to 50:50, andpreferably 95:5 to 65:35.

Any anionic initiator can be employed to initiate the formation andpropagation of the living polymers. Exemplary anionic initiatorsinclude, but are not limited to, alkyl lithium initiators such asn-butyl lithium, arenyllithium initiators, arenylsodium initiators,N-lithium dihydro-carbon amides, aminoalkyllithiums, and alkyl tinlithiums. Other useful initiators include N-lithiohexamethyleneimide,N-lithiopyrrolidinide, and N-lithiododecamethyleneimide as well asorganolithium compounds such as the tri-alkyl lithium adducts ofsubstituted aldimines and substituted ketimines, and N-lithio salts ofsubstituted secondary amines. Exemplary initiators are also described inthe following U.S. Pat. Nos. 5,332,810, 5,329,005, 5,578,542, 5,393,721,5,698,646, 5,491,230, 5,521,309, 5,496,940, 5,574,109, 5,786,441, andInternational Publication No. WO 2004/020475, which are incorporatedherein by reference.

The amount of initiator employed in conducting anionic polymerizationscan vary widely based upon the desired polymer characteristics. In oneembodiment, from about 0.1 to about 100, and in other embodiments fromabout 0.33 to about 10 mmol of lithium per 100 g of monomer is employed.

Anionic polymerizations may be conducted in a polar solvent such astetrahydrofuran (THF), or in a nonpolar hydrocarbon such as the variouscyclic and acyclic hexanes, heptanes, octanes, pentanes, their alkylatedderivatives, and mixtures thereof, as well as benzene.

In order to promote randomization in copolymerization and to controlvinyl content, a polar coordinator may be added to the polymerizationingredients. These randomizers may be used in amounts between 0 and 90or more equivalents per equivalent of lithium. The amount may depend onthe amount of vinyl desired, the level of styrene employed and thetemperature of the polymerization, as well as the nature of the specificpolar coordinator (modifier) employed. Suitable polymerization modifiersinclude, for example, ethers or amines to provide the desiredmicrostructure and randomization of the comonomer units.

Compounds useful as polar coordinators include those having an oxygen ornitrogen heteroatom and a non-bonded pair of electrons. Examples includedialkyl ethers of mono and oligo alkylene glycols; “crown” ethers;tertiary amines such as tetramethylethylene diamine (TMEDA); linear THFoligomers; and the like. Specific examples of compounds useful as polarcoordinators include tetrahydrofuran (THF), linear and cyclic oligomericoxolanyl alkanes such as 2,2-bis(2′-tetrahydrofuryl) propane,di-piperidyl ethane, dipiperidyl methane, hexamethylphosphoramide,N—N′-dimethylpiperazine, diazabicyclooctane, dimethyl ether, diethylether, tributylamine and the like. Linear and cyclic oligomeric oxolanylalkane modifiers are described in U.S. Pat. No. 4,429,091, which isincorporated herein by reference.

Anionically polymerized living polymers can be prepared by either batchor continuous methods. A batch polymerization may be begun by charging ablend of monomer(s) and normal alkane solvent to a suitable reactionvessel, followed by the addition of the polar coordinator (if employed)and an initiator compound. The reactants can be heated to a temperatureof from about 20 to about 130° C. and the polymerization may be allowedto proceed for from about 0.1 to about 24 hours. This reaction canproduce a reactive polymer having a reactive or living end. In one ormore embodiments, at least about 30% of the polymer molecules contain aliving end, in other embodiments at least about 50% of the polymermolecules contain a living end, and in other embodiments at least about80% contain a living end.

The functionalizing agent can be reacted with the living polymer end.This reaction can be achieved by simply mixing the functionalizing agentwith the living polymer. In one embodiment, the functionalizing agentcan be added once a peak polymerization temperature, which is indicativeof nearly complete monomer conversion, is observed. Because live endsmay self-terminate, it may be desirable to add the functionalizing agentwithin about 25 to 35 minutes of the peak polymerization temperature.

The amount of functionalizing agent employed to prepare thefunctionalized polymers can be best described with respect to theequivalents of lithium or metal cation within the initiator.Accordingly, where a lithium initiator is employed, the moles offunctionalizing agent per mole of lithium can be about 0.3 to about 2,in other embodiments from 0.6 to about 1.5, in other embodiments fromabout 0.7 to about 1.3, and in other embodiments from at least about 0.8to about 1.1.

In certain embodiments of this invention, the functionalizing agent canbe employed in combination with other coupling or terminating agents.The combination of functionalizing agent with other terminating agent orcoupling agent can be in any molar ratio. The coupling agents that canbe employed in combination with the functionalizing agent include any ofthose coupling agents known in the art including, but not limited to,tin tetrachloride, tetraethyl ortho silicate, and tetraethoxy tin, andsilicon tetrachloride. Likewise, any terminating agent can be employedin combination with the functionalizing agent including, but not limitedto, tributyltin chloride.

After formation of the functional polymer, a processing aid and otheroptional additives such as oil can be added to the polymer cement. Thefunctional polymer and other optional ingredients can then isolated fromthe solvent and dried. Conventional procedures for desolventization anddrying may be employed. In one embodiment, the functional polymer may beisolated from the solvent by steam desolventization or hot watercoagulation of the solvent followed by filtration. Residual solvent maybe removed by using conventional drying techniques such as oven dryingor drum drying. Alternatively, the cement may be directly drum dried.

After formation of the functional polymer, a processing aid and otheroptional additives such as oil can be added to the polymer cement. Thefunctional polymer and other optional ingredients can then be isolatedfrom the solvent and preferably dried. Conventional procedures fordesolventization and drying may be employed. In one embodiment, thefunctional polymer may be isolated from the solvent by steamdesolventization or hot water coagulation of the solvent followed byfiltration. Residual solvent may be removed by using conventional dryingtechniques such as oven drying or drum drying. Alternatively, the cementmay be directly drum dried.

The functionalized polymers of this invention are useful in preparingtire components. These tire components can be prepared by using thefunctionalized polymers of this invention alone or together with otherrubbery polymers. Other rubbery elastomers that may be used includenatural and synthetic elastomers. The synthetic elastomers typicallyderive from the polymerization of conjugated diene monomers. Theseconjugated diene monomers may be copolymerized with other monomers suchas vinyl aromatic monomers. Other rubbery elastomers may derive from thepolymerization of ethylene together with one or more α-olefins andoptionally one or more diene monomers.

Useful rubbery elastomers include natural rubber, syntheticpolyisoprene, polybutadiene, polyisobutylene-co-isoprene, neoprene,poly(ethylene-co-propylene), poly(styrene-co-butadiene),poly(styrene-co-isoprene), and poly(styrene-co-isoprene-co-butadiene),poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene),polysulfide rubber, acrylic rubber, urethane rubber, silicone rubber,epichlorohydrin rubber, and mixtures thereof. These elastomers can havea myriad of macromolecular structures including linear, branched andstar shaped. Other ingredients that are typically employed in rubbercompounding may also be added.

The rubber compositions may include fillers such as inorganic andorganic fillers. The organic fillers include carbon black and starch.The inorganic fillers may include silica, aluminum hydroxide, magnesiumhydroxide, clays (hydrated aluminum silicates), and mixtures thereof.

A multitude of rubber curing agents may be employed, including sulfur orperoxide-based curing systems. Curing agents are described in 20Kirk-Othmer, Encyclopedia of Chemical Technology, 365-468, (3^(rd) Ed.1982), particularly Vulcanization Agents and Auxiliary Materials,390-402, and A. Y. Coran, Vulcanization in Encyclopedia of PolymerScience and Engineering, (2^(nd) Ed. 1989), which are incorporatedherein by reference. Vulcanizing agents may be used alone or incombination.

Other ingredients that may be employed include accelerators, oils,waxes, scorch inhibiting agents, processing aids, zinc oxide, tackifyingresins, reinforcing resins, fatty acids such as stearic acid, peptizers,and one or more additional rubbers.

These stocks may be useful for forming tire components such as treads,subtreads, black sidewalls, body ply skins, bead filler, and the like.In one or more embodiments, the functional polymers of this inventionare employed in tread formulations, and these tread formulations mayinclude from about 10 to about 100% by weight of the functional polymerbased on the total rubber within the formulation, in other embodiments,the tread formulation may include from about 35 to about 90% by weight,and in other embodiments from about 50 to 80% by weight of thefunctional polymer based on the total weight of the rubber within theformulation. The preparation of vulcanizable compositions and theconstruction and curing of the tire may not be affected by the practiceof this invention.

The vulcanizable rubber composition can be prepared by forming aninitial masterbatch that includes the rubber component and filler. Thisinitial masterbatch can be mixed at a starting temperature of from about25° C. to about 125° C. with a discharge temperature of about 135° C. toabout 180° C. To prevent premature vulcanization (also known as scorch),this initial masterbatch may exclude any vulcanizing agents. Once theinitial masterbatch is processed, the vulcanizing agents can beintroduced and blended into the initial masterbatch at low temperaturesin a final mix stage, which may not initiate the vulcanization process.Optionally, additional mixing stages, sometimes called remills, can beemployed between the masterbatch mix stage and the final mix stage.Rubber compounding techniques and the additives employed therein aregenerally known as disclosed in Stephens, The Compounding andVulcanization of Rubber, in Rubber Technology (2^(nd) Ed. 1973). Themixing conditions and procedures applicable to silica-filled tireformulations are also well known as described in U.S. Pat. Nos.5,227,425, 5,719,207, 5,717,022, and European Patent No. 890,606, all ofwhich are incorporated herein by reference.

Where the vulcanizable rubber compositions are employed in themanufacture of tires, these compositions can be processed into tirecomponents according to ordinary tire manufacturing techniques includingstandard rubber shaping, molding and curing techniques. Typically,vulcanization can be effected by heating the vulcanizable composition ina mold; e.g., it is heated to about 140 to about 180° C. Cured orcrosslinked rubber compositions may be referred to as vulcanizates,which generally contain three-dimensional polymeric networks that arethermoset. In one or more embodiments, the vulcanizate includes avulcanized residue or vulcanization product of the functionalizedpolymer. The other ingredients, such as processing aides and fillers,may be evenly dispersed throughout the vulcanized network. Pneumatictires can be made as discussed in U.S. Pat. Nos. 5,866,171, 5,876,527,5,931,211, and 5,971,046, which are incorporated herein by reference.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES Experiment 1

A living polymer cement was prepared by charging a 5-gallon reactor with4.5 Kg of technical hexanes, 1.23 Kg of a 33% solution of styrene/hexaneblend, and 7.82 Kg of a 21% 1,3-butadiene/hexane blend. A polarrandomizer (about 0.33 equivalents per equivalent of lithium) andn-butyllithium initiator (11 mL of a 1.68 molar solution) weresubsequently charged. The reactor was heated in batch mode to 50° C. Thereaction exotherm to 65° C. within 30 minutes and the reaction was thenstirred for an additional 20 minutes. The resulting cement was thenapportioned to bottles that were dried, nitrogen purged, and ultimatelycapped for subsequent termination reaction.

A first bottle of polymer cement was employed to prepare a control(Sample 1). Isopropyl alcohol was used to both terminate and coagulatethe polymer. The coagulated polymer was then drum dried.

Experiment 2

A second bottle prepared in Experiment 1 was employed to form afunctionalized polymer. Specifically, 0.9 equivalent of tri-n-butoxyborane per equivalent of lithium was added to the bottle and the bottlewas then agitated for 30 minutes at 50° C. The functionalized polymerwas then coagulated in isopropyl alcohol and drum dried.

Experiment 3

Using similar living polymer to that prepared in Experiment 1, a livingpolymer sample (Sample 3) was terminated with 0.9 equivalent oftri-t-butoxy borane per equivalent of lithium and agitated at 50° C. for30 minutes. The terminated polymer was coagulated in isopropyl alcoholand drum dried.

Experiment 4

Using similar living polymer to that prepared in Experiment 1, a livingpolymer sample (Sample 4) was terminated with 0.9 equivalent oftriphenoxy borane per equivalent of lithium and agitated at 50° C. for30 minutes. The terminated polymer was coagulated in isopropyl alcoholand drum dried.

Experiment 5

Using similar living polymer to that prepared in Experiment 1, a livingpolymer sample (Sample 5) was terminated with 0.9 equivalent oftrimethylboroxine per equivalent of lithium and agitated at 50° C. for30 minutes. The terminated polymer was coagulated in isopropyl alcoholand drum dried.

Experiment 6

The functionalized polymers prepared above were each employed to prepareseparate tire formulations that included either a carbon blackreinforcement or a silica and carbon black blend reinforcement. Therecipes for the tire formulations are set forth in Table I.

TABLE I Carbon Black Mixed Silica Ingredient Formulation (phr)Formulation (phr) Functionalized Polymer 100 100 Carbon Black 55 35Silica — 30 Antiozonant 0.95 0.95 Zinc Oxide 2.5 2.5 Stearic Acid 2 1.5Oil 10 10 Wax 1 1.03 Coupling Agent — 2.74 Binder — 0.8 Sulfur 1.3 1.7Accelerator 1.9 2.0 Scorch Inhibitor — 0.25

The tire formulations were mixed using conventional mixing procedures.Namely, when preparing formulations that included carbon blackreinforcement, the ingredients (excluding the sulfur and accelerators)were initially mixed at about 134° C. and the sulfur and acceleratorswere subsequently added in a separate mixing step that was conducted atabout 63° C. Where the formulations included both carbon black andsilica, the ingredients (excluding sulfur, accelerators, binder,coupling agents, and wax) were mixed at about 168° C., the couplingagent was subsequently added and mixed at about 137° C., and the sulfur,accelerators, and wax were added in a subsequent mixing step and mixedat about 95° C.

The formulations were then prepared into test specimens and cured withina closed cavity mold under pressure for 15 minutes at 171° C. The testspecimens were then subjected to various physical tests, and the resultsof these tests are reported in Table II for the formulations thatexclusively included carbon black as a reinforcement and in Table IIIfor the formulations that included a carbon black/silica blend. Theformulation numbers set forth in Tables II and III correspond to theSample numbers of the functionalized polymers above, and those employedin carbon black recipes include the designation “A” and those employedin carbon black/silica formulations include the designation “B.”

TABLE II Formulation 1A 2A 3A 4A 5A ML₁₊₄ @ 130° C. 24.9 31.2 28.0 27.728.6 300% Modulus @ 23° C. (MPa) 11.19 11.21 10.99 11.55 10.61 TensileStrength @ 23° C. (MPa) 16.26 17.06 16.66 17.01 16.69 Temperature Sweep0° C. tan δ 0.2317 0.2601 0.2470 0.2299 0.2430 Temperature Sweep 50° C.tan δ 0.2664 0.2396 0.2628 0.2611 0.2631 ΔG′ (MPa) 4.1178 1.3859 2.87843.51 2.7211 50° C. RDA Strain sweep (5% strain) tan δ 0.2639 0.17270.2247 0.2372 0.2237 Bound Rubber (%) 12.6 31.6 31.6 23.4 22.7

TABLE III Formulation 1B 2B 3B 4B 5B ML₁₊₄ @ 130° C. 59.2 66.5 64.9 76.165.6 300% Modulus @ 23° C. (MPa) 8.1 8.5 8.5 8.5 8.6 Tensile Strength @23° C. (MPa) 11.6 12.0 11.8 12.0 12.5 Temperature Sweep 0° C. tan δ0.1963 0.2021 0.1989 0.1902 0.1999 Temperature Sweep 50° C. tan δ 0.24260.2239 0.2271 0.2265 0.2289 ΔG′ (MPa) 7.164 5.801 6.603 9.109 5.753 50°C. RDA Strain sweep (5% strain) tan δ 0.2404 0.2082 0.2189 0.2280 0.2225Bound Rubber (%) 21.6 31.4 27.4 27.9 27.3

Mooney viscosity measurement was conducted at 130° C. using a largerotor. The Mooney viscosity was recorded as the torque when the rotorhas rotated for 4 minutes. The sample is preheated at 130° C. for 1minute before the rotor starts.

The bound rubber content test was used to determine the percent ofpolymer bound to filler particles in tire tread stocks. Bound rubber wasmeasured by immersing small pieces of uncured stocks in a large excessof toluene for three days. The soluble rubber was extracted from thesample by the solvent. After three days, any excess toluene was drainedoff and the sample was air dried and then dried in an oven atapproximately 100° C. to a constant weight. The remaining pieces form aweak coherent gel containing the filler and some of the original rubber.The amount of rubber remaining with the filler is the bound rubber. Thebound rubber content is then calculated according to the following:

$\begin{matrix}{{\%\mspace{14mu}{Bound}\mspace{14mu}{Polymer}} = \frac{100\;\left( {{Wd} - F} \right)}{R}} & (1)\end{matrix}$where Wd is the weight of dried gel, F is the weight of filler in gel orsolvent insoluble matter (same as weight of filler in original sample),and R is the weight of polymer in original sample.

The tensile mechanical properties were measured using the standardprocedure described in the ASTM-D 412 at 25° C. and 100° C. The tensiletest specimens had dumbbell shapes with a thickness of 1.9 mm. Aspecific gauge length of 25.4 mm is used for the tensile test. Heat ageddata was obtained after heating the vulcanizates for 24 hours at 100° C.

Temperature sweep experiments were conducted with a frequency of 31.4rad/sec using 0.5% strain for temperature ranging from −100° C. to −10°C., and 2% strain for the temperature ranging from −10° C. to 100° C. ΔGis the change in G′ at 0.25% form G′ at 14.75%. Payne effect (ΔG′) datawere obtained from the strain sweep experiment. A frequency of 3.14rad/sec was used for strain sweep which is conducted at 50° C. withstrain sweeping from 0.25% to 14.75%.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A tire component comprising: a vulcanized residue of a functionalizedpolymer defined by the formula I

where π is a rubbery polymer chain, B is a boron atom, R¹ is a bond or adivalent organic group, and each υ is independently selected from alkoxygroups (—OR), where each R is independently selected from monovalentorganic groups or two R groups form a divalent organic group, whichforms a cyclic structure.
 2. The tire component of claim 1, where thefunctionalized polymer is defined by the formula 1A

where π is a polymer chain, R¹ is a bond or a divalent organic group, Bis a boron atom, O is an oxygen atom, and each R² is independently amonovalent organic group or two R² groups join to form a divalentorganic group, which forms a cyclic structure.
 3. The tire component ofclaim 1, where π is a rubbery polymer that has a glass transitiontemperature that is less than 0° C.
 4. The tire component of claim 3,where π is a rubbery polymer selected from polybutadiene, polyisoprene,poly(styrene-co-butadiene), poly(styrene-co-butadiene-co-isoprene),poly(isoprene-co-styrene), and poly(butadiene-co-isoprene).
 5. The tirecomponent of claim 3, where the rubbery polymer has a number averagemolecular weight of from about 5 to 1,000 Kg/mol.
 6. The tire componentof claim 1, where the functionalized polymer is defined by the formulaII

where α is a functionality or functional group that reacts or interactswith rubber or rubber fillers or otherwise has a desirable impact onfilled rubber compositions or vulcanizates, π is a polymer chain, B is aboron atom, and υ is independently selected from alkoxy groups (—OR),where each R is independently selected from monovalent organic groups ortwo R groups form a divalent organic group, which forms a cyclicstructure.
 7. The tire component of claim 1, where the functionalizedpolymer is prepared by terminating a living polymer with an organoboroncompound.
 8. The tire component of claim 7, where the organoboroncompound is defined by the formula IIIR ³ _(3-n) B(

)_(n) where each

is independently selected from alkoxy groups (—OR), where each R isindependently a monovalent organic group or two R groups form a divalentorganic group, which forms a cyclic structure, each R³ is independentlya monoorganic group, a halide, or two R³ groups form a divalent organicgroup, which forms a cyclic structure, and n is an integer from 1 to 3.9. The tire component of claim 8, where the organoboron compoundincludes alkoxyboranes and mixes thereof.
 10. The tire component ofclaim 9, where the organoboron compound is tri-n-butoxyborane.
 11. Thetire component of claim 9, where the organoboron compound istri-t-butoxyborane.
 12. The tire component of claim 9, where theorganoboron compound is triphenoxyborane.
 13. The tire component ofclaim 9, where the organoboron compound is trimethylboroxineborane. 14.The tire component of claim 7, where the tire component is a tire tread.15. A tire component prepared by a process comprising: vulcanizing arubber formulation comprising a vulcanizable rubber and a filler, wherethe vulcanizable rubber includes a functionalized polymer that isdefined by the formula I

where π is a rubbery polymer chain, B is a boron atom, R¹ is a bond or adivalent organic group, and each υ is independently selected from alkoxygroups (—OR), where each R is independently selected from monovalentorganic groups or two R groups form a divalent organic group, whichforms a cyclic structure.